Internal combustion engine fuel system



United States Patent [72] Inventor Donald D. Stoltman Henrietta, NewYork [21] Appl. No. 701,482

[22] Filed Jan. 29, 1968 Continuation of Ser. No. 450,038, Apr. 22, 1965[45] Patented Sept. 22, 1970 [73] Assignee General Motors CorporationDetroit, Michigan a corporation of Delaware [54] INTERNAL COMBUSTIONENGINE FUEL SYSTEM 2 Claims, 7 Drawing Figs.

[52] U.S.C1 123/119, 261/23, 261/39, 261/52 [51] Int. Cl. F02m l/10,F02m 11/06 [50] Field ofSearch 261/23.1,

[56] References Cited UNITED STATES PATENTS 2,702,536 2/1955 Carlson..123/119(F)UX 2,939,445 6/1960 Sterner 261/39(.2)UX 2,943,848 7/1960Gordon et a1... 261/39(.2)UX

....123/ll9(F)UX 129/1 19(F)UX 261/39 2,956,558 10/ l 960 Sterner et al.2,957,465 10/1960 Wagner 3,321,193 5/1967 I-lighley PrimaryExaminerRonald R. Weaver Ait0rneysA. F. Baillio, J. L. Carpenter and C.K. Veenstra period and to delay release of the secondary stage throttlefrom the lockout member. A throttle valve is rotatably disposed in theair inlet to control air flow therethrough. A lever arm is connected tothe throttle valve for rotation therewith in a certain path. A throttlecontrol mechanism having a member with a cam surface disposed in thepath for contact with the lever arm. The cam surface variably limitsclosing movement of the lever arm and the throttle valve to establish arange of minimum throttle openings. A choke valve is disposed in theair-inlet and a thermostatic member responsive to engine operatingtemperatures is connected to the choke valve to control air flow pastthe. choke valve only over a first range of temperatures. The throttlecontrol mechanism has a linkage moved by the thermostatic member formoving and controlling the position of the cam surfaced member over arange of temperatures including a second range of temperatures higherthan those of the first range. The thermostatic member and the linkageprovide a control for the cam surfaced member to permit a decreasedminimum throttle opening upon an increase in temperature. The linkageincludes a lever disposed for movement in an arcuate path. In oneembodiment a baffle is located adjacent the lever and the baffle has anarcuate slot adjacent the arcuate path. The baffle has first and secondapertures with an elongated spring member having one end received andsubstantially immobilized in the first aperture. The spring member hasan intermediate portion received and supported in a second aperture. Thespring member having the end opposite the one end supported by theintermediate portion in a cantilevered manner and extending through thearcuate slot into the arcuate path of movement of the lever for contacttherewith. The opposite end of the spring member is disposed to contactthe lever only as the mechanism is moved by the thermostatic memberwithin the second range of temperatures. Contact of the opposite end ofthe spring member with the lever providing a force opposing movement ofthe throttle control mechanism by the thermostatic member for delayingmovement of the mechanism and thereby delaying a decrease in the minimumthrottle opening. 1n another embodiment the linkage includes a leverdisposed for movement in an arcuate path and a shaft connected to thelever. An elongated spring member is substantially immobilized at oneend and having an intermediate portion coiled about and supported by theshaft. The spring member having the end opposite one end supported bythe intermediate portion in a cantilevered manner and extending into thearcuate path of movement of the lever for contact therewith. Theopposite end of the spring is disposed to contact the lever only as themechanism is moved by the thermostatic member within the second range oftemperatures. Contact of the opposite end of the spring member with thelever providing a force opposing movement of the throttle controlmechanism by the thermostatic member for delaying movement of themechanism and thereby delaying a decrease in the minimum throttleopening.

Patented Sept. 22, 1970 3,529,555

Sheet 1 012 I 1\" VENTOR.

' 59022042 59. SIB/fwd ATTOK/VE) INTERNAL COMBUSTION ENGINE FUEL SYSTEMThis application is a continuation of application Ser. No. 450,038,filed Apr. 22, 1965 and now abandoned.

This invention pertains to mechanism for controlling the throttle of aninternal combustion engine fuel system and is particularly directed tomeans for extending the period of time during which throttle valveposition is affected by a thermostatic control.

Most of the carburetors on automotive engines include a fast idle camwhich holds the throttle valve open in varying degrees during the enginewarm-up period. Such an arrangement admits sufficient air to the engineto increase the idling speed and prevent engine stalling during warm-up.The fast idle cam is generally controlled by the choke thermostat and isgradually released as the choke thermostat allows the choke valve toopen. However, it is often desirable to completely open the choke valvesooner than the fast idle cam may be released to allow the throttlevalve to close. Earlier proposals to achieve such a result have involveda linkage arrangement which now appears to be of unnecessary complexity.For example, see US. Pat. No. 2,957,465 issued in the name ofC. L.Wagner.

This invention provides a much simpler arrangement for accomplishing thesame result which uses means for resisting movement of the thermostatlinkage beyond that portion of its movement which controls air flow. Insome carburetors, it can make use of the fact that the choke valverestricts air flow through the mixture conduits only during the initialportion of its opening movement. During the final portion of the chokevalve opening movement the venturi, throttle valve and throttle valveopening provides a greater restriction to air flow than that caused bythe choke valve. This invention slows the choke thermostat openingmovement during that portion of its movement which controls this finalportion of choke valve opening movement. Thus the fast idle cam, whichis controlled by the choke thermostat, does not release the throttlevalve to close completely for an extended period of time.

To slow the opening movement of the choke thermostat, a spring isinterposed in the path of movement of a portion of the linkage in orderto resist movement of the linkage during the final opening movement. Thechoke operating linkage may be modified so that the thermostat assistsair flow through the mixture conduit and actively pulls the choke open.As the thermostat pulls in the choke opening direction, it will meet theresistance of the spring. Thus the rate of opening movement will bereduced during the final portion of opening movement, and the fast idlecam will hold the throttle valve open for a longer period of time.

In multi-stage fuel systems wherein air inlets or mixture conduits aresequentially opened, it is often desirable to delay opening of thesecondary throttle valve controlling the secondary inlet or conduituntil the choke in the primary air inlet is completely open. Mechanismhas been proposed which will lock out the secondary throttle valve toprevent opening during choke valve opening movement. Such mechanismoccasionally is combined with or operates in conjunction with thepreviously discussed fast idle cam and is released to unlock thesecondary throttle valve only when the choke valve is fully opened.However, it is often desirable to completely open the choke valve soonerthan the secondary throttle may be unlocked. This invention, inproviding means to slow the final choke thermostat opening movement whenair flow is not affected, delays release of the secondary throttle valvelockout mechanism for an extended period of time.

The details as well as other objects and advantages of this inventionare disclosed in the following description and in the drawings in which:

FIG. 1 is a side elevational view of a carburetor including oneembodiment of this invention;

FIG. 2 is an enlarged view of a portion of FIG. 1, with parts brokenaway to show the embodiment in greater detail;

FIG. 3 is a perspective view of the baffle plate often used in automaticchoke mechanisms and showing the spring mounted on the baffle plate;

FIG. 4 is a view along line 4-4 of FIG. 1;

FIG. 5 is a view along line 5-5 of FIG. 4;

FIG. 6 is a view of an alternative embodiment of this invention in whichthe choke thermostat is located remotely from the carburetor; and

FIG. 7 is a view along line 7-7 of FIG. 6.

FIG. 1 illustrates a four-barrel, multi-stage carburetor 10 havingprimary and secondary mixture conduits I2 and 14 respectively. A chokevalve 16 is pivotally mounted in the inlet to primary mixture conduitsl2 and throttle valves 18 and 20 are rotatably disposed at the outlet ofmixture conduits l2 and 14 respectively.

As shown in greater detail in FIGS. 2, 4, and 5, a choke thermostathousing 22 is mounted on legs 24, 26, and 28 extending from carburetor10. A bolt 30 secures housing 22 to carburetor 10. Housing 22 is dividedinto two chambers 32 and 34 by a baffle plate 36. A coiled bimetalthermostat 38 is mounted in the outer chamber 32 with its inner endsecured to the cover plate 42 for housing 22. Cover plate 42 has afitting 44 to which a conduit may be secured for conveying heated airinto housing 22 from a stove on the exhaust manifold (not shown).

The outer free end of thermostat 38 is secured to a tang 46 of a lever48 mounted in the other chamber 34. Tang 46 extends through an arcuateslot 50 provided in baffle 36.

A passage 52 is provided through leg 28 to subject chamber 34 to themanifold vacuum which exists in mixture conduit 12 below throttle 18.The vacuum will draw heated air through fitting 44 on cover plate 42,over thermostat 38 in chamber 32, and through slot 50 in baffle 36. Asthermostat 38 is warmed, it will uncoil to rotate lever 48 in theclockwise direction.

Lever 48 is secured to a shaft 54 which exte.-..ls through the rear ofhousing 22 into carburetor 10. A lever so is secured to the other end ofshaft 54 and operates link 58 which is connected to a lever 60 securedto the ChOKc valve shaft 62. Thus as the temperature of thermostat 38Changes, its outer free end rotates lever 48, shaft 54, and lever 56 andthrough link 58 and lever 60 positions choke valve 16.

FIG. 5 illustrates a linkage arrangement for controlling the primary andsecondary throttles in accordance with temperature changes. As discussedabove, it is often necessary to limit closing of primary throttles 18 tomaintain a higher idling speed when the engine is cold. in addition,secondary throttles 20 should be prevented from opening when the engineis cold.

As shown in FIG. 5, a lever 64 is secured to the primary throttle shaft66 and carries an adjusting screw 68. A second lever 70 is rotatablymounted on primary throttle shaft 66 and is gravitationally biasedcounterclockwise to remain in contact with adjusting screw 68. Asprimary throttles l8 rotate in the clockwise direction to close,adjusting screw 68 pushes lever 70 in the clockwise direction until itcontacts a fast idle cam member 72 and prevents further closure ofthrottles 18. Fast idle cam member 72 is rotatably mounted upon shaft54.

A pin 76 is carried by shaft 54 and extends through a slot 78 in member72. A large mass 80 on the end of member 72 gravitationally biasesmember 72 so that the end 82 of slot 78 rests against pin 76. Asthermostat 38 is warmed, shaft 54 and pin 76 will be rotated clockwiseto allow member 72 to also rotate clockwise.

When primary throttles 18 are opened and levers 64 and 70 rotatecounterclockwise, member 72 will be free to follow shaft 54 and pin 76so that the cam will be appropriately positioned whenever throttles 18are closed. If, on the other hand, primary throttles 18 are closed whilethe thermostat 38 is warmed, the force of the throttle return spring(not shown) transmitted through primary throttle shaft 66 and lever 64will hold lever 70 against cam 72 with sufficient force to preventrotation of member 72. As the thermostat is warmed, shaft 54 and pin 76will rotate away from the end 82 of slot 78. When primary throttles 18are later opened, member 72 will rotate due to its gravitational biasand catch up with pin 76.

A tang 84 on lever 64 is adapted to engage an arm 86 on lever 70 torotate lever 70 clockwise as primary throttles 18 approach wide open.Arm 86 will engage a protrusion 88 on member 72 to rotate member 72clockwise. The clockwise motion of member 72 will be transmitted throughpin 76, shaft 54, lever 56, link 58 and lever 60 (see FIG. 4) to open orunload the choke valve 16.

A lever 90 is rotatably mounted upon leg 24 and is gravitationallybiased clockwise to engage a pin 92 carried by the secondary throttleshaft 94. Lever 90 prevents rotation of pin 92 and thus prevents openingof the secondary throttles 20. As thermostat 38 warms and members 72rotates clockwise, a protrusion 96 on member 72 engages an arm 98 oflever 90 to rotate lever 90 out of engagement with pin 92, therebyunlocking the secondary throttles.

[n the illustrated carburetor construction, the choke blade 16 ceases torestrict air fiow before it reaches a wide open position. This has beenattributed to the fact that the air-flow area offered by the venturis100 in the primary mixture conduits 12 or the air-flow area about wideopen primary throttles I 18 is less than the total area opened by thechoke blade 16. Therefore, during its final opening movement, the chokevalve 16 offers no restriction to air flow.

Since this final opening movement offers no restriction to air flow,such final opening movement may be retarded without adversely affectingthe operating characteristics of the automatic choke. This inventionretards the final opening movement of the choke to extend the period inwhich the primary throttles 18 are held open by the fast idle cam member72 and the secondary throttles 20 are locked in a closed position by thelockout lever 90.

Referring to FIGS. 2 and 3, a wire spring 102 is secured through a pairof holes 104 and 106 in baffle 36. A tang 108 on the end of spring 102extends through the slot 50 and is disposed in the path of tang 46 andthe free end of thermostat 38. The notch 109 in baffle 36 fits over aprotrusion 110 within housing 22 to properly align baffle plate 36 andspring 102 with respect to the movement of thermostat 38. As thermostat38 is warmed and its free end, together with tang 46 on lever 48, movesin a clockwise direction, it will encounter the resistance of spring102. The movement of thermostat 38 and lever 48 will be retarded byspring 102 until the force of thermostat 38 is sufficient to overcomethe force of spring 102. The free end of thermostat 38 will then move inan opening direction at a reduced rate.

The reduced rate of movement of thermostat 38 results in a slowing ofthe final opening movement of choke thermostat 38 and choke valve 16 andwill extend the period of operation before primary throttles 18 arereleased from the fast idle cam member 72 and will also delay therelease of secondary throttles 20 from the lockout lever 90.

The apparatus shown in F I65. 6 and 7 illustrates an alternativeembodiment of the apparatus contained in housing 22. In some situationsit is desirable to mount thermostat 38 remotely from carburetor 10, in astove within the exhaust manifold or in the water manifold asschematically illustrated at l l 1.

In this alternative embodiment, the thermostat 38 drives a link 112 tooperate a lever 114 secured to the shaft 54. Shaft 54 is in all otherrespects identical with that earlier described with reference to FIGS. 4and 5. Shaft 54 extends from carburetor through a bracket 116 spacedfrom carburetor 10 upon legs 24, 26, and 28. Bracket 116 is secured tocarburetor 10 by bolt 30.

A wire spring 118 is coiled about shaft 54 and is retained under tensionby tangs 120 and 122 bent outwardly from bracket 116.

As the thermostat 38' is warmed, it will force link 112 upwardly torotate lever 114 and shaft 54 in a clockwise direction. Near the end ofthe choke opening movement, a tang 124 on lever 114 engages spring 118.Spring 118 stops the choke thermostat and choke valve opening movementuntil the force of thermostat 38' is sufficient to overcome the force ofspring 118. Thermostat 38 will then open choke valve 16 at a reducedrate. This alternative embodiment will thus slow the final chokethermostat and choke valve opening movement to delay the release ofprimary throttles 18 from fast idle cam member 72 and delay theunlocking of secondary throttles 20 from lever 90.

l claim:

1. An internal combustion engine fuel system comprising an inlet for airflow to the engine, a throttle valve rotatably disposed in said inlet tocontrol air flow therethrough, a lever arm connected to said throttlevalve for rotation therewith, said lever arm rotating in a certain path,a throttle control mechanism, said mechanism having a member with a camsurface disposed in said path for contact with said lever arm, said camsurface providing means for variably limiting closing movement of saidlever arm and said throttle valve to establish a range of minimumthrottle openings, a choke valve disposed in said inlet to control airflow therethrough, a thermostatic member responsive to engine operatingtemperatures, means for connecting said choke valve to said thermostaticmember to control air flow past said choke valve only over a first rangeof temperatures, said throttle control mechanism also having linkagemeans moved by said thermostatic member for moving and controlling theposition of said cam surfaced member over a range of temperaturesincluding a second range of temperatures higher than those of said firstrange whereby said thermostatic member and said throttle controlmechanism provide means to control the minimum throttle opening over arange of temperatures including said second range, said thermostaticmember and said linkage means providing means for controlling said camsurfaced member to permit a decreased minimum throttle opening upon anincrease in temperature, said linkage means including a lever disposedfor movement in an arcuate path, a baflle located adjacent said lever,said baffle having an arcuate slot adjacent said arcuate path, saidbaffie further having first and second apertures, an elongated springmember having one end received and substantially immobilized in saidfirst aperture, said spring member having an intermediate portionreceived and supported in said second aperture, said spring memberhaving the end opposite said one end supported by said intermediateportion in a cantilevered manner and extending through said arcuate slotinto the arcuate path of movement of said lever means for contacttherewith, said opposite end being disposed to contact said lever meansonly as said mechanism is moved by said thermostatic member within saidsecond range of temperatures, contact of said opposite end of saidspring member with said lever means providing a force opposing movementof said throttle control mechanism by said thermostatic member fordelaying movement of said mechanism and thereby delaying a decrease inthe minimum throttle opening.

2. An internal combustion engine fuel system comprising an inlet for airflow to the engine, a throttle valve rotatably disposed in said inlet tocontrol air flow therethrough, a lever arm connected to said throttlevalve for rotation therewith, said lever arm rotating in a certain path,a throttle control mechanism, said mechanism having a member with a camsurface disposed in said path for contact with said lever arm, said camsurface providing means for variably limiting closing movement of saidlever arm and said throttle valve to establish a range of minimumthrottle openings, a choke valve disposed in said inlet to control airflow therethrough, a thermostatic member responsive to engine operatingtemperatures, means for connecting said choke valve to said thermostaticmember to control air flow past said choke valve only over a first rangeof temperatures, said throttle control mechanism also having linkagemeans moved by said thermostatic member for moving and controlling theposition of said cam surfaced member over a range of temperaturesincluding a second range of temperatures higher than those of said firstrange whereby said thermostatic member and said throttle controlmechanism provide means to control the minimum throttle opening over arange of temperatures including said second range, said thermostaticmember and said linkage means providing means for controlling said camsurfaced member to permit a decreased minimum throttle opening upon anincrease in temperature, said linkage means including a lever meansdisposed for movemechanism is moved by said thermostatic member withinsaid second range of temperatures, Contact of said opposite end of saidspring member with said lever means providing a force opposing movementof said throttle control mechanism by said thermostatic member fordelaying movement of said mechanism and thereby delaying a decrease inthe minimum throttle opening.

